SYNOPSIS

DESCRIPTION

The usleep() function suspends execution of the calling process for (at
least) usec microseconds. The sleep may be lengthened slightly by any
system activity or by the time spent processing the call or by the
granularity of system timers.

RETURN VALUE

None (BSD). Or: 0 on success, -1 on error (SUSv2).

ERRORS

EINTR Interrupted by a signal.
EINVAL usec is not smaller than 1000000. (On systems where that is
considered an error.)

CONFORMING TO

4.3BSD, POSIX.1-2001. The SUSv2 version returns int, and this is also
the prototype used by glibc 2.2.2. Only the EINVAL error return is
documented by SUSv2.

NOTES

The type useconds_t is an unsigned integer type capable of holding
integers in the range [0,1000000]. Programs will be more portable if
they never mention this type explicitly. Use
#include <unistd.h>
...
unsigned int usecs;
...
usleep(usecs);
This type is defined by <sys/types.h> included by <unistd.h> but glibc
defines it only when _XOPEN_SOURCE has a value not less than 500, or
both _XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED are defined.
The interaction of this function with the SIGALRM signal, and with
other timer functions such as alarm(), sleep(), nanosleep(),
setitimer(), timer_create(), timer_delete(), timer_getoverrun(),
timer_gettime(), timer_settime(), ualarm() is unspecified.
This function is obsolete. Use nanosleep(2) or setitimer(2) instead.